The technique utilizing a coupling reaction is important for the synthesis of electronic materials, intermediates for medicines and pesticides, and various functional compounds. Among others, a technique utilizing a coupling reaction wherein a boron-containing compound is allowed to react with an organic halide compound in the presence of a base and a catalyst attracts widespread attention (which reaction is hereinafter referred to as “Suzuki coupling reaction” when appropriate) as a broadly applicable synthesis technique. In recent years, Suzuki coupling reaction has become very important for the synthesis of biaryl compounds for use as intermediates for medicines and pesticides and as a material for liquid crystal, and synthesis of substituted olefin compounds for use as a raw material for functional materials.
Heretofore, the synthesis of biaryl compounds and substituted olefin compounds according to Suzuki coupling reaction has been widely carried out using a catalyst comprised of a palladium salt and a phosphine compound (hereinafter abbreviated to as “palladium-phosphine catalyst”). However, palladium is expensive and, when less expensive raw materials such as chlorides are used for the cross-coupling reaction using the palladium-phosphine compound, the reaction does not proceed at a desired rate.
As less expensive substitutes for the expensive palladium-phosphine catalyst, catalysts each comprised of a nickel salt and a phosphine compound (hereinafter abbreviated to as “nickel-phosphine catalyst”) has been proposed in, for examples, Japanese Unexamined Patent Publication (hereinafter abbreviated to as “JP-A”) 2000-302697, JP-A 2000-302720, JP-A 2003-119175 and JP-A 2004-91467; and Tetrahedron Letters, England, 1996, vol. 37, p 2993-2996 (see scheme 1, tables 1 and 2), Journal of Organic Chemistry, USA, 1997, vol. 62, p 8024-8030 (see scheme 1, Tables 1-6), and Tetrahedron Letters, England, 1997, vol. 38, p 3513-3516 (see scheme 1, tables 1 and 2). However, these proposed catalysts have problems such that a phosphine ligand such as 1,2-bis(diethylphosphino)ethane which is expensive and has poor stability and poor handling properties must be used in combination with a nickel compound for carrying out the reaction with good efficiency, and occasionally a reducing agent such as butyllithium which is also expensive and has poor handing properties must be used.
Recently, a catalyst comprised of a nickel compound with an amine compound (hereinafter referred to as “nickel-amine compound”) attracts attention (for example, JP-A 2004-91465 and Tetrahedron, England, 1999, vol. 55, p 11889-11894 (see FIG. 1-FIG. 3, tables 1-3). This catalyst has a problem such that an expensive amine compound such as 1,8-diazabicyclo[5.4.0]-7-undecene must be used in combination with said catalyst to enhance the yield to a desired level, and that bis(1,5-cyclooctadiene)nickel as used as the nickel compound is very sensitive to air and difficult to handle in the air, and thus, is not suitable for commercial use.
Further, nickel catalysts commonly have a problem such that a strong base such as potassium phosphate must be used in combination with the nickel catalyst which is expensive and tends to cause decomposition reaction of a boronic acid raw material.